Influence of protozoa on the process of nitrogen fixation by Azotobacter Chroococcum

SUMMARY 1 Increased nitrogen fixation by Azotobacter chroococcum in the presence of protozoa, as shown by Nasir, has been confirmed 2 The same effect is found, using soil as a medium. 3 There is a definite relationship between the efficiency of the strain used, the incubation period and the concentration of mannitol employed. 4 The feeding action of Colpidium colpoda and Hartmanella hydlina on Azotobacter has been demonstrated. 5 The reason for increased nitrogen fixation appears to be due to the efficiency of Azotobacter being maintained for a longer period.